The invention relates to a method for the pyrolysis and gasification of organic substances or mixtures of organic substances and to an apparatus for carrying out such a method.
A series of methods are known for the treatment and utilisation of organic substances and mixtures of organic substances by, for example, gasification and pyrolysis. The methods differ according to the oxidation or reduction gas used and according to the type of contact between the solid and the gas. In solid bearing or gas bearing a distinction is made between, among others, a circulating fluidised-bed gasifier, an entrained-bed gasifier, a rotary furnace gasifier and a moving-bed gasifier with counterflow gas bearing, co-current gas bearing or cross-flow gas bearing. The majority of known gasification methods is not suitable for smaller, decentralised systems due to the high apparatus effort. Smaller, decentralised systems are advisable in particular when biomass is used as the application material.
The operating behaviour of gasification methods in accordance with the principle of the circulating fluidised bed is highly dependent on the respective particle size household of the fluidised bed consisting of the application material to be gasified and the also circulating inert material. Corresponding demands result from this on the unit size of the application material. Extremely higher demands on the preparation of the fuel result in the case of entrained-bed gasification which only allows the use of pulverised fuel particles.
Further substantial disadvantages of the known gasification methods are that the proceeding process stages of drying, degassing, gasification and incineration of the application material proceed in zones which are directly next to one another and which merge into one another. As a result, the individual zones within a reactor are undefined and the degassing, gasification and incineration can proceed incompletely at points. In further known methods, an attempt is made to eliminate these disadvantages by the separation of the individual process stages proceeding at the fuel of degassing, gasification and incineration.
In DE 197 20 331 A1, a method and an apparatus for the gasification or incineration of dry or damp, fine-particle or fragmentary biomass and of waste are proposed in which due to the hot walls of an incinerator and due to the inflow of hot waste gas from the incinerator into a degassing furnace, biological raw materials degas in this, whereby coke and pyrolysis gas are produced, with the coke arriving at the glow bed of the gasification reactor after passing the shredder, whereas the pyrolysis gas burns in the incineration chamber of the gasification reactor under the supply of a limited amount of air and the waste gas produced subsequently flows through the glow bed of the gasification reactor in which an oxidation of the carbon to CO takes place with a simultaneous reduction of waste gas (CO2) and steam (H2O) to a combustible lean gas (CO, H2). Due to the fact that the pyrolysis is carried out due to the heating because of the contact with hot combustion waste gases and that furthermore a partial incineration of the pyrolysis gas is carried out, only a product gas with a low calorific value can be produced with the method proposed in DE 197 20 331 A1. When fuels with a high content of volatile components and a low pyrolysis coke yield are used, there is a risk of an insufficient formation of the glow bed of the gasification reactor consisting of pyrolysis coke, whereby the oxidation of the carbon to CO with a simultaneous reduction of waste gas and steam to a combustible lean gas proceeds insufficiently at the cost of the product gas calorific value.
A method is furthermore known from U.S. Pat. No. 4,568,362 for the gasification of organic substances and mixtures of organic substances in which the organic substances are led into a pyrolysis reactor in which the organic substances come into contact with a heat transfer medium, whereby a rapid pyrolysis takes place which transforms the organic substances into pyrolysis products which consist of pyrolysis gases with condensable substances and a solid carbonaceous residue and the required heating energy for the pyrolysis is produced by incinerating the solid carbonaceous residue in a combustion reactor and in a second reaction zone of the pyrolysis reactor, the pyrolysis gases containing tar are subjected to such crack reactions and reactions with steam that a product gas with a high calorific value is obtained. In these methods, both the pyrolysis and the incineration of the solid carbonaceous residue take place in a fluidised bed. A reaction zone for the pyrolysis gases containing tar is provided in the upper part of the pyrolysis fluidised bed. The operation of the fluidised beds requires a high effort and a control of the reactions of the pyrolysis gases in the reaction zone is hardly possible.
The German patent application 197 77 693.0 of older priority and not pre-published, on which the German patent DE 197 55 693 C1 has been granted, discloses a method for the gasification of organic substances and mixtures of organic substances.
It is the underlying object of the invention to provide a method which is simple to carry out for the pyrolysis and gasification of organic substances or mixtures of organic substances and an apparatus to generate a gas with a high calorific value.